LOS ANGELES — Chinese star pianist Lang Lang figured he had enough to worry about for his Grammy Awards collaboration with Metallica — mastering a tricky piano accompaniment to the band’s labyrinth classic “One,” performing his newly created role as the Grammys’ ambassador to China and attending all the obligatory social functions while battling a cold — so he settled on an outfit early.

Then he saw first-hand how the grizzled members of the metal institution dressed. And so it was that, less than 24 hours before the 31-year-old was to begin his amble down the red carpet and take part in not one but two primetime performances, Lang Lang was absorbed in yet another fitting at his elegant suburban Los Angeles hotel.

“I am still trying out different outfits,” he lamented with a laugh at the Pasadena, Calif., hotel’s lounge on Saturday, clad in a blazer and a bright blue T-shirt with jeans. “For the red carpet and for the Tchaikovsky concerto, I’m going to wear the grey Armani suit. (But) when we started rehearsing, I saw all the guys from Metallia are having a very different style. So I’m thinking, maybe I should look into something else.

“So the stylist is actually in my room now and we’re trying to figure it out. Because I don’t want to look like a foreigner to the band. We need to look like one band.”

Indeed, the Grammys performance means very much to Lang Lang. He even notes that he got a haircut, though to the untrained eye his sloping coif seems to reach, as ever, for the ceiling (the New Yorker once noted that the animated pianist looks like a “porcupine in a typhoon” when he plays).

Although it wasn’t until the gifted instrumentalist moved to Philadelphia as a high-school student that he was able to see the Grammys, the show was on his radar before that as a youth in China, where the show didn’t then air. (“Of course we all know Grammys because all the most famous musicians are always showing off their Grammys,” he recalled with a laugh. “So we all know the trophy.”)

Sunday’s broadcast will be aired on TV in Shanghai and radio in Beijing, and Lang Lang notes that his appearance is already causing a bit of a stir there — he points out that enterprising fans online seamlessly edited together a “very funny” band shot of Metallica that includes the piano phenom.

The Grammys, too, are counting on Lang Lang. He regards Recording Academy president Neil Portnow as one of his “best friends” and Lang Lang says the Grammys are focusing significant attention on China, eventually hoping to potentially establish a regional award show similar to the Latin Grammys. In 2008 — the same year he was both a first-time nominee and took the stage with his idol Herbie Hancock — Lang Lang even went on a trip with Portnow to Beijing.

“We had a great time,” he recalled. “I showed him some foot massage places.”

Also top of mind for the gifted, unconventional pianist is that classical artists rarely get a chance to bask in the spotlight at music’s most prominent awards bash (he points out with sad resignation that the classical categories are never included in the broadcast, something he learned when first nominated), so he feels he has an opportunity to deliver a message to fans about the relevance of his beloved genre.

So he’s the Grammys’ ambassador to China and classical’s ambassador to viewers. A lot of pressure perhaps, and he admits he was “a bit overwhelmed” at the amount of press that greeted the announcement of his performance with Metallica. Given that he wasn’t sure how seamlessly it would come together, he was nervous that it would disappoint.

But once he gathered with the band, he said, such concerns faded from view.

“We’ve had two rehearsals, and already I think this is the coolest thing I’ve ever done,” he said.

He remembers the first time he heard Metallica, cruising around with a friend in Madrid following one of his concerts, roughly eight years ago.

“Suddenly this heavy metal stuff comes on and I said: ‘This is a really cool thing … what is this?’ They said, ‘That’s Metallica,”‘ he says, drawing out the syllables for emphasis. “I thought, wow, that’s cool.”

Metallica, meanwhile, has been away from the Grammys for 22 years, says drummer Lars Ulrich. When the organization approached the legendary band about performing, Ulrich said they immediately suggested a collaboration with Lang Lang — perhaps an appropriate pairing given that the band had just pulled off a successful tour of China last year.

Until days before the Grammys, Ulrich said they’d merely spoken with Lang Lang over the phone. Once they met, he was blown away.

“He’s great,” Ulrich said Friday in the bowels of the Staples Center, while rehearsals carried on nearby. “He’s got so much energy and character and personality and he really kind of exudes musical ability. It makes up for our lack of that.

“It’s a good balance,” he adds with a sly smile. “He’s insane. He’s absolutely insanely great.”

“They play incredibly precise,” he replies emphatically. “Lars, he’s amazing. We have such eye contact while we’re performing. And the rest of the guys … they are phenomenal to work with. It feels like we are old friends for a long time. It just really has that feeling.”

Lang Lang has long sought to stoke a passion in young listeners who find it difficult to relate to classical (he famously recorded a short video of himself playing Chopin by rolling an orange around on the keys that soon went viral).

Asked about the connection between the centuries-old compositions he usually plays and the pulverizing metal he’s contributing to this weekend, his eyes light up.

“The forms are directly what we do in classical music,” he said. “You have the beginning and then slightly softer and then the improvisation part and it goes into the singing part — everything’s very organized. And not repeating, that’s another thing. Sometimes when you do pop music or hip hop or rock and roll, it repeats the same thing. In this one, there’s not even two bars they play the same. It’s always going, going, going. That’s kind of classical music. You’re always trying to make a ton of operations.”

Of course, Lang Lang has proven his ability to rise to big moments. He’s performed for nearly every distinguished dignitary the world over, including U.S. President Barack Obama, the Queen and Chinese President Hu Jintao, he’s faced audiences in most legendary musical venues the world has to offer and he played the openings of both the 2006 FIFA World Cup and the 2008 Beijing Olympics.

Still, he’s approached his Grammy gig with a winning sense of wonder, for instance tweeting a grinning photo of himself lording over the Staples Center placards marking where Jay Z and Beyonce were to sit at Sunday’s ceremony. He says the Grammys are “equally as important” as those Beijing Olympics.

And perhaps more tiring. He mentions his busy week — which included Clive Davis’s famous soiree and the MusiCares Person of the Year bash — with a mix of awe and just a hint of weariness.

“You come here, you better prepare (to) party long,” he said with a laugh. “Because this is the place. The last two days, I was having a cold, so I was not feeling so well. Today, I’m totally fine. So I’m ready for the parties.”